Fate mapping reveals the age structure of the peripheral T cell compartment

Significance The development of the peripheral T cell pool is typically described based on the maturation and survival of cells in the periphery, assuming all cells are created equal and have similar lifespans. We have developed a mouse model in which we can “timestamp” CD8 + T cells produced at different ages and track their survival. We find that cells produced early in life persist and contribute to the adult pool. However, the dynamics of cell survival are dependent on the age at which they are produced, leading to a shifting population of cells with age. We propose that heterogeneity in the developmental origins of cells contributes to the phenotypic heterogeneity of individual cells observed in adult animals.